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%I #6 Nov 21 2013 12:48:13
%S 8,68,3072,393212,167772152,257698037748,1477743627730928,
%T 32281802128991715308,2720083094132915643088872,
%U 891316828285473797927369441252,1142305308877662078276709192428421088,5749410871496176278677177367167155700760540,113997127711810427619887416951870075533162738352088
%N 4*(2^(n^2-n+1)*(n^2-n)-n+3).
%D A. J. Hoffman, On eigenvalues of symmetric (+1, -1) matrices, Israel J. Math., 17 (1974), 69-75 (MR 50#2202).
%t f[n_]:=Module[{n2n=n^2-n},4 (2^(n2n+1) n2n-n+3)]; Array[f,15] (* _Harvey P. Dale_, Mar 24 2011 *)
%K nonn
%O 0,1
%A _N. J. A. Sloane_, Oct 24 2003